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(n) Best friends sister syndrome - a diease that results from dating your best friends sister. Symptoms- your best friends sister seems hotter than usual and you have the urge to ask her out. Warning may result in death in some rare cases
Dude, your totally going to get BFSS from dating his sister.
by Gil Jacobson January 13, 2010

Words related to BFSS

best dating diease friend hot sister syndrome